1. Field of the Invention
Embodiments of the present invention relate to a driving device for a semiconductor element that drives a semiconductor element composing a power conversion apparatus, for example, and has a protection operation discriminating function.
2. Description of the Related Art
A related type of driving device for a semiconductor element is disclosed in Japanese Unexamined Patent Application Publication No. H08-070580 (also referred to herein as “Patent Document 1”), for example. The driving device comprises an alarm circuit that is provided for an intelligent power module (IPM) that is a power transistor module for driving an inverter, and comprises an overcurrent alarm means, an overvoltage alarm means, and an overheat alarm means.
In the conventional example disclosed in Patent Document 1, the overcurrent alarm means outputs a first alarm signal having a first pulse width upon detection of an overcurrent state of a power transistor; the overvoltage alarm means outputs a second alarm signal having a second pulse width on detection of an overvoltage state at an output terminal of the power transistor; and the overheat alarm means outputs a third alarm signal having a third pulse width on detection of an overheat state of the power transistor. As a result, detection of the pulse width of the outputted alarm signal is sufficient to discriminate among an overcurrent state, an overvoltage state, and an overheat state.
Another driving device for a semiconductor element is disclosed in Japanese Unexamined Patent Application Publication No. 2002-027665 (also referred to herein as “Patent Document 2”). The driving device in an intelligent power module comprises: necessary number of semiconductor switching elements, a driving circuit, various types of detection circuits for detecting serious abnormality and precursor abnormality of the switching elements and the driving circuit, and warning circuits corresponding to the detection circuits, an abnormality detecting logic circuit for protection operation of the switching elements upon detection of abnormality by these detection circuits, a control circuit for externally outputting the signals based on the abnormality detection signals, and a transmission circuit.
In the conventional example disclosed in Patent Document 2, the transmission circuit has an output terminal that outputs an alarm signal upon detection of serious abnormality and an output terminal that outputs an abnormality factor discrimination signal indicating factors for the serious abnormality and the precursor abnormality. Preferably, these two types of terminals are shared to form a single common output terminal.
Japanese Unexamined Patent Application Publication No. 2000-341960 (also referred to herein as “Patent Document 3”) discloses another intelligent power module that is a semiconductor device comprising, in an integrated body, IGBTs composing a power conversion bridge circuit of the inverter apparatus, an IGBT 1DB for switching a current for dissipating regenerative electric power of a motor in a regenerative resistance, and a pre-driver containing driving circuits and protective circuits for respective IGBTs. The protective circuit of the driving device for a semiconductor element in the intelligent power module outputs an alarm signal ALM1 in an abnormal condition through an alarm enable line to outside of the intelligent power module. However, prior to the alarm ALM1, the protective circuit outputs a precaution alarm ALM2 through a precaution alarm line to outside of the intelligent power module without shut-down of the IGBT when discrimination of precursor to abnormality occurrence is made based on detection of a collector current in the IGBT or a chip temperature that is a predetermined value higher than the normal value but lower than a level to issue the alarm ALM1.
In the conventional example disclosed in Patent Document 1, individual detection is made on overcurrent abnormality, overvoltage abnormality and overheat abnormality in the power transistors composing the inverter, and first, second and third alarm signals having different pulse widths are outputted externally. Consequently, detection of pulse width allows discrimination among the overcurrent abnormality, overvoltage abnormality and overheat abnormality. However, each of the overcurrent alarm means, overvoltage alarm means, and the overheat alarm means functions as a one-shot multi-vibrator upon detection of the overcurrent abnormality, an overvoltage abnormality, or overheat abnormality and outputs one alarm signal with a predetermined pulse width. As a result, if an alarm signal is outputted from any other alarm means simultaneously with the alarm means in operation or before the alarm signal of the alarm means in operation returns to ON state, an alarm signal is erroneously detected. That is one of unsolved problems.
The conventional example disclosed in Patent Document 2 needs to output two types of signals of an alarm signal and an abnormality factor discriminating signal, which results in a complicated structure of a signal forming circuit. That is another unsolved problem.
In the conventional example disclosed in Patent Document 3, the protection circuit outputs an alarm ALM1 externally through an alarm enable line on an event of abnormality. The protection circuit makes a decision that a sign of generating an abnormality is detected when the collector current of an IGBT or the chip temperature exceeds a predetermined level which is higher than a normal level but lower than an abnormal level to deliver the alarm ALM1 and outputs a precaution alarm ALM2 externally through a precaution alarm line. This protection circuit cannot make discrimination between collector current abnormality and chip temperature abnormality, but only determines that the IGBT is in a condition where an abnormality has been generated or there exist a sign of generating an abnormality. Thus, the device of Patent Document 3 cannot make discrimination among abnormality factors. That is another largely unsolved problem.